Has anyone noticed that adding an invisible token on some npcs does not work?

I.e. npcRef.addItem invisibleToken 1
Then check their inventory, and it's not there.

This happens particularly with the Fighter's Guild porter and on guards.

Anyone know the cause and how to work around it?

Maybe do a GetItemCount after the AddItem and if it's 0 add another one? GetItemCount will atleast show if it's added at all.

I use my Actor Details.esp utility to check for inventory.
I'm not really sure why the AddItem doesn't stick with some NPCs yet.
It could be because the items are set to no equippable "slot" or maybe that I am using AddItemNS.
Some NPCs do receive the item, however.
Weirrrd...gonna try to investigate this fully tognight.